Standalone water purification systems, which have been commercially available for decades, are used principally in laboratory environments to provide highly purified and high quality reagent grade water for various applications, including the field of chemical analysis and physical testing. Water purification systems for these applications purify water by a number of well-known techniques, including filtration, single or multiple distillation, sorption, and ion exchange. Ordinary tap water contains a variety of impurities, including dissolved organics, dissolved inorganics, dissolved gases, suspended particles, microorganisms, and byproducts from bacterial degradation that must be removed using a water purification system to generate reagent grade water.
The purity of reagent water is graded according to various standards, including the commonly-accepted standard D1193-99el “Standard Specification for Reagent Water” established by the organization ASTM International (West Conshohocken, Pa.) and setting forth requirements for water suitable for use in methods of chemical analysis and physical testing. Under this familiar standard, the highest quality reagent water conforms to, or exceeds, ASTM Type I standards and is generally used in applications like high performance liquid chromatography (HPLC), atomic absorption (AA) spectrometry, and tissue culture. The ASTM Type II grade of reagent water, which has a lower purity than ASTM Type I reagent water, may be used for hematological, serological, and microbiological procedures. Reagent water suitable for general laboratory qualitative analyses, such as urinalysis, parasitology, and histological procedures, conforms to ASTM Type III standards. The ASTM Type IV grade of reagent water has the least stringent standards and is used in applications where these relaxed purity requirements are permitted.
Conventional water purification systems may include a purification unit that contains a pump that moves water under pressure through a fluid circuit and a water purification device capable of removing unwanted contaminants from water circulating in the fluid circuit. The water purification unit includes a manually-operated tap or dispensing valve positioned at a convenient location on the water purification unit that diverts purified water from the fluid circuit for fixed dispensing.
Certain applications dictate the need for a capability of dispensing water remote from the water purification unit. To extend the range of operation, in addition to the normal manually-operated dispensing valve, a separate and independent dispensing gun may be connected to the water purification unit by a length of flexible tubing that transports purified water from the water purification unit to the remote dispensing gun. The dispensing gun may be positioned relative to the stationary water purification unit within the spatial limits imposed by the length of the flexible tubing for remotely dispensing purified water.
Use of a remote dispensing gun in a water purification system also conserves space on the bench-top because the water purification unit can be positioned, for example, either under the bench, at the back of the bench, or high on a wall. In certain designs, the remote dispensing gun is removably supported in a bracket integrated into the purification unit and may be optionally used for fixed dispensing local to the purification unit when mounted in the bracket. When removed from the bracket and hand held to dispense purified water into a container, the remote dispensing gun must be gripped at all times while depressing a gun trigger or with the gun trigger locked.
Other remote dispensing guns include a wall-mounting bracket that holds the dispensing gun for fixed dispensing. Such wall-mounted brackets may include an articulated swing arm with rigid arm segments coupled by joints. One end of the swing arm is coupled with the bracket and the opposite end carries the dispensing gun. The swing arm can be extended from the bracket to physically separate the dispensing gun away from the wall. The dispensing gun may also be removed from the bracket and held for non-fixed dispensing.
Still other conventional water purification systems include a stand, which is a distinct support structure from the water purification unit, that sits on the bench top and supports the remote dispensing gun for fixed dispensing. These stands may include an articulated arm with multiple rigid segments united for relative movement by joints and a bracket for holding the dispensing gun positioned at the end of the articulated arm. Such stands are passive structures and do not include any electrical components for flow control or manifolds. A stream of purified water is continuously circulated through the tubing coupling the water purification unit with the dispensing gun and through the dispensing gun. When the dispensing gun is manually actuated, purified water is dispensed.
In another mode of operation, the remote dispensing gun may be locked in the opened position and purified water is supplied from the water purification unit for a time specified at the water purification unit. After the time lapses, water flow from the water purification unit to the remote dispensing gun is completely discontinued and the water purification unit is placed into a state in which water is no longer circulated. Any residual purified water remaining in the tubing coupling the water purification unit with the dispensing gun, in the dispensing gun, and in the fluid circuit inside the water purification unit is stagnant. The absence of circulation promotes bacterial growth and causes leaching from internal surfaces wetted by the static water. To reestablish water flow, a user must manually close the dispensing gun and restart the water purification unit.
In light of these and other problems in the art, it would be desirable to provide a remote dispensing device with local flow logic that cooperates with flow logic in the water purification unit to regulate water flow at the remote dispensing device.